Traveling-wave tubes are capable of amplifying and generating microwave signals over a considerable frequency range (e.g., 1-90 GHz) with relatively high output powers (e.g., >10 megawatts), relatively large signal gains (e.g., 60 dB), and over relatively broad bandwidths (e.g., >10%).
In a traveling-wave tube, an electron gun generates a beam of electrons that are directed through a slow-wave structure and collected by a collector. The electron gun generates the beam of electrons by creating an electrical potential between a cathode and an anode. Electrons emitted from the cathode are accelerated towards the anode by the electrical potential between the anode and cathode. The slow-wave structure generally comprises either a helical conductor or a coupled cavity circuit with signal input and output ports located at opposite ends of the structure. The electron beam is directed into an opening of the slow-wave structure, through the slow-wave structure, and out another opening in the slow-wave structure. A beam-focusing structure surrounding the slow-wave structure creates an axial magnetic field that contains the electron beam within the slow-wave structure.
A microwave signal applied to one of the ports propagates along the slow-wave structure to the other port at a projected axial velocity that is considerably less than the free space speed of light. With the velocity of the electron beam adjusted to be similar to the projected axial velocity of the microwave signal propagating along the slow-wave structure, the fields of the microwave signal and electron beam interact with one another so as to transfer energy from the electron beam to the microwave signal, thereby amplifying the microwave signal.
A traveling-wave tube may be used as an amplifier by coupling a microwave signal to the signal input port of the slow-wave structure. The microwave signal propagates towards the signal output port in the same direction as the electron beam and becomes amplified by extracting energy from the electron beam. As a result of this energy exchange, the electron beam loses energy which reduces the velocity of the electron beam.
Traveling-wave tubes sometimes also include a second anode located between the cathode and the traveling-wave tube and that is used as an ion trap. During operation, the electron beam ionizes residual gas molecules in the traveling-wave tube. The ions produced drift towards the electron gun and are accelerated towards the cathode where they contaminate the cathode and interfere with operation of the system. The ion trap is used to repel the ions generated to prevent the ions from bombarding the cathode, thus preventing premature aging of the cathode and/or reduction in system performance.
One problem with some prior art traveling-wave tube systems is that they do not include an ion trap. Another problem with some prior art traveling-wave tube systems is that they do not have a power supply suitable to operate the ion trap.
A need therefore exists for systems and methods for providing traveling-wave tubes with an ion trap and suitable source of power to operate the ion trap.